Method and apparatus for handling a beam failure recovery in wireless communication system

ABSTRACT

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates beyond 4th-Generation (4G) communication system such as long term evolution (LTE). A terminal in a wireless communication system is provided. The terminal includes a transceiver, and at least one processor configured to receive, from a base station (BS), a beam failure recovery configuration comprising at least one reference signal for identifying a candidate beam for the beam failure recovery and associated random access (RA) parameters, identify the candidate beam for the beam failure recovery using the at least one reference signal, and perform a physical random access channel (PRACH) using the at least one reference signal and the associated RA parameters on the candidate beam for the beam failure recovery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/638,127 filed on Feb. 10, 2020, which is a 371 of InternationalApplication No. PCT/KR2018/009152 filed on Aug. 10, 2018, which claimspriority to India Patent Application No. 201741028536 filed on Aug. 10,2017, and India Patent Application No. 201741028536 filed on Jun. 4,2018, the disclosures of which are herein incorporated by reference intheir entirety.

BACKGROUND 1. Field

The present disclosure generally relates to a wireless communicationsystem. More specifically, this disclosure relates to a method and anapparatus for handling a beam failure recovery in the wirelesscommunication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5th generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution(LTE) System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as toaccomplish higher data rates. To decrease propagation loss of the radiowaves and increase the transmission distance, the beamforming, massivemultiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, large scale antenna techniquesare discussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadratureamplitude modulation (FQAM) and sliding window superposition coding(SWSC) as an advanced coding modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

Generally, mobile communication systems have been developed forproviding a high quality mobile communication services to a user. Withthe dramatic development of communication technologies, the mobilecommunication systems are now capable of providing high-speed datacommunication services as well as voice communication services. A LongTerm Evolution (LTE) is a technology for implementing a packet-basedcommunication at a higher data rate of a maximum of about 100 Mbps. Inorder to meet the demand for an increased wireless data traffic, sincedeployment of 4^(th) generation (4G) communication systems, efforts havebeen made to develop an improved 5^(th) generation (5G) communicationsystems or a LTE-Advanced communication system. Therefore, the 5G orLTE-Advanced communication system is also called a ‘beyond 4G network’or a ‘post LTE system’. The 4G communication systems operate in sub-6GHz spectrum bands, where all transmissions and receptions take place inan Omni-directional manner.

In order to achieve a high data transmission rate, the 5G communicationsystem is considered to be implemented in a millimeter wave (mm Wave) orextremely higher frequency bands as well, for e.g., 28 GHz, 60 GHz,etc., so as to accomplish higher data rates. For achieving the higherfrequency bands, it has been shown that a beam forming is necessary fora successful communication to be performed as shown in FIG. 5 . In suchinstance, a random access procedure is performed for providing acommunication between a User Equipment (UE) and a Base Station (BS). TheUE performs an initial access procedure by scanning for PrimarySynchronization Signal (PSS), Secondary Synchronization Signal (SSS) andthen becoming synchronized in a downlink. Upon synchronization, therandom access procedure is performed in order to acquire an uplinksynchronization for performing uplink transmissions appropriately.

Further, the UE is configured to monitor a radio link for determining aquality of the downlink (DL) in order to continue with a transmission.As the 5G communication system operates in the millimeter waves, theremay cause a sudden blockage in the radio link then, the UE may notreceive a signal from the BS. Hence, there is a need for the UE todetermine that there exists the beam failure and perform the beamfailure recovery procedure.

Thus, it is desired to address the above mentioned disadvantages orother shortcomings or at least provide a useful alternative.

SUMMARY

Embodiments of the present disclosure provide a method and an apparatusfor handling a beam failure recovery in a wireless communication system.

Embodiments of the present disclosure provide a method and apparatus forconfiguring by a BS a beam failure recovery configuration include atleast one reference signal for identifying a candidate beam for the beamfailure recovery and associated Random Access (RA) parameters.

Embodiments of the present disclosure provide a method and apparatus forindicating the beam failure recovery configuration to a UE for the beamfailure recovery.

Embodiments of the present disclosure provide a method and apparatus forconfiguring the beam failure recovery configuration for any one of aContention-Free Random Access Physical Random Access Channel (CFRAPRACH) and a Contention-Based Random Access Physical Random AccessChannel PRACH (CBRA PRACH).

Embodiments of the present disclosure provide a method and apparatus foridentifying by the UE the candidate beam for the beam failure recoveryusing the at least one reference signal.

Embodiments of the present disclosure provide a method and apparatus forperforming by the UE a PRACH using the at least one reference signal andthe associated RA parameters on the candidate beam for the beam failurerecovery.

Embodiments of the present disclosure provide a method and apparatus fordetecting whether a beam failure recovery response is received from theBS.

Embodiments of the present disclosure provide a method and apparatus foridentifying whether other candidate beam for the beam failure recoveryis available.

Embodiments of the present disclosure provide a method and apparatus fordetermining whether a timer value is expired for performing the beamfailure recovery.

Embodiments of the present disclosure provide a method and apparatus fordetermining whether a maximum retransmission limit for sending the PRACHfor the beam failure recovery is met.

Embodiments of the present disclosure provide a method and apparatus forperforming the PRACH using reference signal and the associated RAparameters on the other candidate beam for the beam failure recovery,when the timer value and the maximum retransmission limit is notexpired.

Embodiments of the present disclosure provide a method and apparatus fortriggering a Radio Link Failure (RLF), when the timer value and themaximum retransmission limit has expired.

In one embodiment, a method for handling a beam failure recovery in awireless communication system is provided. The method includesconfiguring, by a BS, a beam failure recovery configuration include atleast one reference signal for identifying a candidate beam for the beamfailure recovery and associated Random Access (RA) parameters. Further,the method includes indicating, by the B S, the beam failure recoveryconfiguration to a UE for the beam failure recovery.

In another embodiment, the at least one reference signal is one of aSynchronization Signal (SS) block and a Channel State InformationReference Signal (CSI-RS).

In yet another embodiment, the associated RA parameters include a RACHpreamble, RACH resources in a time domain and a frequency domain, atimer value, a maximum retransmission limit, a power ramping value and aRandom Access Response (RAR) window response configuration and preambleindices.

In yet another embodiment, the beam failure recovery configuration isconfigured for any one of a Contention-Free Random Access PhysicalRandom Access Channel (CFRA PRACH) and a Contention-Based Random AccessPhysical Random Access Channel PRACH (CBRA PRACH).

Accordingly embodiments herein provide a method for handling a beamfailure recovery in a wireless communication system. The method includesreceiving, by a UE, a beam failure recovery configuration include atleast one reference signal for identifying a candidate beam for the beamfailure recovery and associated RA parameters from a BS. Further, themethod includes identifying, by the UE, the candidate beam for the beamfailure recovery using the at least one reference signal. Furthermore,the method includes performing, by the UE, a PRACH using the at leastone reference signal and the associated RA parameters on the candidatebeam for the beam failure recovery.

In yet another embodiment, the CFRA PRACH or the CBRA PRACH to beperformed is identified based on the associated Random Access (RA)parameters configured to the UE on the candidate beam for the beamfailure recovery.

In yet another embodiment, the CFRA PRACH is performed using the SSblock as the reference signal and the associated RA parameters on thecandidate beam for the beam failure recovery.

In yet another embodiment, the CFRA PRACH is performed using the CSI-RSas the reference signal and the associated RA parameters on thecandidate beam for the beam failure recovery.

In yet another embodiment, the CFRA PRACH is performed using the CSI-RSas the reference signal and the associated RA parameters on thecandidate beam for the beam failure recovery and further performing thePRACH by using the SS block as the reference signal and the associatedRA parameters on the candidate beam for the beam failure recovery.

In yet another embodiment, the CBRA PRACH is performed using the SSblock as the reference signal and the associated RA parameters on thecandidate beam for beam failure recovery.

In yet another embodiment, the candidate beam is identified based on aReference Signal Received Power (RSRP) threshold configured for the beamfailure recovery.

In yet another embodiment, the method further includes detecting, by theUE, whether a beam failure recovery response is received from the BS.Further, the method includes identifying by the UE whether othercandidate beam for the beam failure recovery is available. Further, themethod includes determining by the UE whether a timer value is expiredfor performing the beam failure recovery or a maximum retransmissionlimit for sending the PRACH for the beam failure recovery is met basedon the indication of associated RA parameters. Furthermore, the methodincludes causing by the UE one of:

a. performing, by the UE, a PRACH using reference signal and theassociated RA parameters on the other candidate beam for the beamfailure recovery when the timer value is not expired or the maximumretransmission limit for sending the PRACH for the beam failure recoveryis not met; andb. triggering, by the UE, a Radio Link Failure (RLF) when the timervalue is expired for performing the beam failure recovery or the maximumretransmission limit for sending the PRACH for the beam failure recoveryis met.

In yet another embodiment, the PRACH is one of a CFRA PRACH and a CBRAPRACH.

In yet another embodiment, the CFRA PRACH or the CBRA PRACH to beperformed is identified based on the associated Random Access (RA)parameters configured to the UE on the other candidate beam for the beamfailure recovery.

In yet another embodiment, the CFRA PRACH is performed using the SSblock as the reference signal and the associated RA parameters on theother candidate beam for the beam failure recovery.

In yet another embodiment, the CFRA PRACH is performed using the CSI-RSas the reference signal and the associated RA parameters on the othercandidate beam for the beam failure recovery.

In yet another embodiment, the CFRA PRACH is performed using the CSI-RSas the reference signal and the associated RA parameters on the othercandidate beam for the beam failure recovery and then by using the SSblock as the reference signal and the associated RA parameters on theother candidate beam for the beam failure recovery.

In yet another embodiment, the CBRA PRACH is performed using a SS blockas the reference signal and the associated RA parameters on thecandidate beam for beam failure recovery.

In yet another embodiment, a BS for handling a beam failure recovery ina wireless communication system is provided. The BS includes a beamfailure recovery engine coupled with a memory and a processor. The beamfailure recovery engine configures a beam failure recovery configurationinclude at least one reference signal for identifying a candidate beamfor the beam failure recovery and associated Random Access (RA)parameters. Further, the beam failure recovery engine is configured toindicate the beam failure recovery configuration to a UE for the beamfailure recovery.

In yet another embodiment, a UE for handling a beam failure recovery ina wireless communication system is provided. The UE includes a beamfailure recovery engine coupled with a memory and a processor. The beamfailure recovery engine is configured to receive a beam failure recoveryconfiguration include at least one reference signal for identifying acandidate beam for the beam failure recovery and associated RAparameters from a BS. Further, the beam failure recovery engine isconfigured to identify a candidate beam for the beam failure recoveryusing the at least one reference signal. Furthermore, the beam failurerecovery engine is configured to perform a PRACH using the at least onereference signal and the associated RA parameters on the candidate beamfor the beam failure recovery.

In yet another embodiment, a base station (BS) in a wirelesscommunication system is provided. The base station includes at least oneprocessor configured to configure a beam failure recovery configurationcomprising at least one reference signal for identifying a candidatebeam for beam failure recovery and associated random access (RA)parameters; and a transceiver configured to: transmit, to the terminal,the beam failure recovery configuration, and receive, from the terminal,a random access preamble for the beam failure recovery which istransmitted on the identified candidate beam.

In yet another embodiment, a terminal in a wireless communication systemis provided. The terminal includes at least one processor; and atransceiver configured to: receive, from a base station (BS), a beamfailure recovery configuration, and transmit, to the BS, a random accesspreamble for the beam failure recovery which is transmitted on theidentified candidate beam, wherein the beam failure recoveryconfiguration comprises at least one reference signal for identifying acandidate beam for beam failure recovery and associated random access(RA) parameters.

In yet another embodiment, a method for operating a base station (BS) ina wireless communication system is provided. The method includesreceiving, from a base station (BS), a beam failure recoveryconfiguration; and transmitting, to the BS, a random access preamble forthe beam failure recovery which is transmitted on the identifiedcandidate beam, wherein the beam failure recovery configurationcomprises at least one reference signal for identifying a candidate beamfor beam failure recovery and associated random access (RA) parameters.

In yet another embodiment, a method for operating a terminal in awireless communication system is provided. The method includesreceiving, from a base station (BS), a beam failure recoveryconfiguration; and transmitting, to the BS, a random access preamble forthe beam failure recovery which is transmitted on the identifiedcandidate beam, wherein the beam failure recovery configurationcomprises at least one reference signal for identifying a candidate beamfor beam failure recovery and associated random access (RA) parameters.

These and other aspects of the embodiments herein will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following descriptions, while indicatingpreferred embodiments and numerous specific details thereof, are givenby way of illustration and not of limitation. Many changes andmodifications may be made within the scope of the embodiments hereinwithout departing from the spirit thereof, and the embodiments hereininclude all such modifications.

A method and an apparatus according to various embodiments of thepresent disclosure allows to cope with a sudden blockage in the radiolink by determining that there exists the beam failure and performingthe beam failure recovery procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

This method is illustrated in the accompanying drawings, throughoutwhich like reference letters indicate corresponding parts in the variousfigures. The embodiments herein will be better understood from thefollowing description with reference to the drawings, in which:

FIG. 1 illustrates a wireless communication system according to variousembodiments of the present disclosure;

FIG. 2 illustrates the BS in the wireless communication system accordingto various embodiments of the present disclosure;

FIG. 3 illustrates the terminal in the wireless communication systemaccording to various embodiments of the present disclosure;

FIG. 4 illustrates the communication interface in the wirelesscommunication system according to various embodiments of the presentdisclosure;

FIG. 5 is an example RACH procedure for beam forming in a 5Gcommunication system, according to a prior art;

FIG. 6 is a block diagram of a wireless communication system in which aBS communicates with a UE, according to an embodiment as disclosedherein;

FIG. 7 is a sequence diagram illustrating various signaling messagescommunicated between the BS and the UE for handling a beam failurerecovery in the wireless communication system, according to anembodiment as disclosed herein;

FIG. 8A is a flow diagram illustrating various operations for handlingthe beam failure recovery in the wireless communication system,according to an embodiment as disclosed herein;

FIG. 8B is a flow diagram illustrating various operations for handlingthe beam failure recovery in the wireless communication system,according to an embodiment as disclosed herein;

FIG. 9 is a flow diagram illustrating various operations performed bythe UE for sending a PRACH for the beam failure recovery, according toan embodiment as disclosed herein;

FIGS. 10A-10C are illustrating a scenario in which a recovery responseis received from the BS for the beam failure recovery, according to anembodiment as disclosed herein;

FIG. 11 is a schematic diagram illustrating multiple preamble formatsfor short sequence length according to various embodiments of thepresent disclosure;

FIG. 12 is a schematic diagram illustrating format A and C according tovarious embodiments of the present disclosure;

FIG. 13 is a schematic diagram illustrating three different allocationswhen format A3 is required according to various embodiments of thepresent disclosure;

FIG. 14 is a schematic diagram illustrating RACH preamble formataccording to presence of GT according to various embodiments of thepresent disclosure;

FIG. 15 is a schematic diagram illustrating usage scenarios for variousformats (A and B) according to various embodiments of the presentdisclosure;

FIG. 16 is a schematic diagram illustrating RACH mapping according tovarious embodiments of the present disclosure; and

FIG. 17 is a schematic diagram illustrating various kinds of RACHmapping according to various embodiments of the present disclosure.

DETAILED DESCRIPTION

Various embodiments of the present disclosure will now be described indetail with reference to the accompanying drawings. In the followingdescription, specific details such as detailed configuration andcomponents are merely provided to assist the overall understanding ofthese embodiments of the present disclosure. Therefore, it should beapparent to those skilled in the art that various changes andmodifications of the embodiments described herein can be made withoutdeparting from the scope and spirit of the present disclosure. Inaddition, descriptions of well-known functions and constructions areomitted for clarity and conciseness.

Also, the various embodiments described herein are not necessarilymutually exclusive, as some embodiments can be combined with one or moreother embodiments to form new embodiments. Herein, the term “or” as usedherein, refers to a non-exclusive or, unless otherwise indicated. Theexamples used herein are intended merely to facilitate an understandingof ways in which the embodiments herein can be practiced and to furtherenable those skilled in the art to practice the embodiments herein.Accordingly, the examples should not be construed as limiting the scopeof the embodiments herein.

As is traditional in the field, embodiments may be described andillustrated in terms of blocks which carry out a described function orfunctions. These blocks, which may be referred to herein as managers,engines, controllers, units or modules or the like, are physicallyimplemented by analog and/or digital circuits such as logic gates,integrated circuits, microprocessors, microcontrollers, memory circuits,passive electronic components, active electronic components, opticalcomponents, hardwired circuits and the like, and may optionally bedriven by firmware and software. The circuits may, for example, beembodied in one or more semiconductor chips, or on substrate supportssuch as printed circuit boards and the like. The circuits constituting ablock may be implemented by dedicated hardware, or by a processor (e.g.,one or more programmed microprocessors and associated circuitry), or bya combination of dedicated hardware to perform some functions of theblock and a processor to perform other functions of the block. Eachblock of the embodiments may be physically separated into two or moreinteracting and discrete blocks without departing from the scope of thedisclosure. Likewise, the blocks of the embodiments may be physicallycombined into more complex blocks without departing from the scope ofthe disclosure.

The term ‘NR’ is “new radio” is the term used by 3GPP specification fordiscussing activities about 5G communication systems.

The term “base station” and “gNB” used herein can be usedinterchangeably without departing from the scope of the embodiments.Further, the term “mapping” and “association” used herein can be usedinterchangeably without departing from the scope of the embodiments.

Hereinafter, in various embodiments of the present disclosure, hardwareapproaches will be described as an example. However, various embodimentsof the present disclosure include a technology that uses both hardwareand software and thus, the various embodiments of the present disclosuremay not exclude the perspective of software.

Hereinafter, the present disclosure describes technology for handling abeam failure recovery in a wireless communication system.

The terms referring to a beam failure recovery configuration, the termsreferring to a candidate beam, the terms referring to a signal, theterms referring to a channel, the terms referring to controlinformation, the terms referring to a network entity, and the termsreferring to elements of a device used in the following description areused only for convenience of the description. Accordingly, the presentdisclosure is not limited to the following terms, and other terms havingthe same technical meaning may be used.

Further, although the present disclosure describes various embodimentsbased on the terms used in some communication standards (for example,3rd Generation Partnership Project (3GPP)), they are only examples forthe description. Various embodiments of the present disclosure may beeasily modified and applied to other communication systems.

FIG. 1 illustrates a wireless communication system according to variousembodiments of the present disclosure. In FIG. 1 , a base station (BS)110, a terminal 120, and a terminal 130 are illustrated as the part ofnodes using a wireless channel in a wireless communication system. FIG.1 illustrates only one BS, but another BS, which is the same as orsimilar to the BS 110, may be further included.

The BS 110 is network infrastructure that provides wireless access tothe terminals 120 and 130. The BS 110 has coverage defined as apredetermined geographical region based on the distance at which asignal can be transmitted. The BS 110 may be referred to as “accesspoint (AP),” “eNodeB (eNB),” “5th generation (5G) node,” “wirelesspoint,” “transmission/reception Point (TRP)” as well as “base station.”

Each of the terminals 120 and 130 is a device used by a user, andperforms communication with the BS 110 through a wireless channel.Depending on the case, at least one of the terminals 120 and 130 mayoperate without user involvement. That is, at least one of the terminals120 and 130 is a device that performs machine-type communication (MTC)and may not be carried by the user. Each of the terminals 120 and 130may be referred to as “user equipment (UE),” “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” or “userdevice” as well as “terminal.”

The BS 110, the terminal 120, and the terminal 130 may transmit andreceive wireless signals in millimeter wave (mmWave) bands (for example,28 GHz, 30 GHz, 38 GHz, and 60 GHz). At this time, in order to improve achannel gain, the BS 110, the terminal 120, and the terminal 130 mayperform beamforming. The beamforming may include transmissionbeamforming and reception beamforming. That is, the BS 110, the terminal120, and the terminal 130 may assign directivity to a transmissionsignal and a reception signal. To this end, the BS 110 and the terminals120 and 130 may select serving beams 112, 113, 121, and 131 through abeam search procedure or a beam management procedure. After that,communications may be performed using resources having a quasico-located relationship with resources carrying the serving beams 112,113, 121, and 131.

A first antenna port and a second antenna ports are considered to bequasi co-located if the large-scale properties of the channel over whicha symbol on the first antenna port is conveyed can be inferred from thechannel over which a symbol on the second antenna port is conveyed. Thelarge-scale properties may include one or more of delay spread, dopplerspread, doppler shift, average gain, average delay, and spatial Rxparameters.

FIG. 2 illustrates the BS in the wireless communication system accordingto various embodiments of the present disclosure. A structureexemplified at FIG. 2 may be understood as a structure of the BS 110.The term “-module”, “-unit” or “-er” used hereinafter may refer to theunit for processing at least one function or operation and may beimplemented in hardware, software, or a combination of hardware andsoftware.

Referring to FIG. 2 , the BS may include a wireless communicationinterface 210, a backhaul communication interface 220, a storage unit230, and a controller 240.

The wireless communication interface 210 performs functions fortransmitting and receiving signals through a wireless channel. Forexample, the wireless communication interface 210 may perform a functionof conversion between a baseband signal and bitstreams according to aphysical layer standard of the system. For example, in datatransmission, the wireless communication interface 210 generates complexsymbols by encoding and modulating transmission bitstreams. Further, indata reception, the wireless communication interface 210 reconstructsreception bitstreams by demodulating and decoding the baseband signal.

In addition, the wireless communication interface 210 up-converts thebaseband signal into an Radio Frequency (RF) band signal, transmits theconverted signal through an antenna, and then down-converts the RF bandsignal received through the antenna into the baseband signal. To thisend, the wireless communication interface 210 may include a transmissionfilter, a reception filter, an amplifier, a mixer, an oscillator, adigital-to-analog convertor (DAC), an analog-to-digital convertor (ADC),and the like. Further, the wireless communication interface 210 mayinclude a plurality of transmission/reception paths. In addition, thewireless communication interface 210 may include at least one antennaarray consisting of a plurality of antenna elements.

On the hardware side, the wireless communication interface 210 mayinclude a digital unit and an analog unit, and the analog unit mayinclude a plurality of sub-units according to operation power, operationfrequency, and the like. The digital unit may be implemented as at leastone processor (e.g., a digital signal processor (DSP)).

The wireless communication interface 210 transmits and receives thesignal as described above. Accordingly, the wireless communicationinterface 210 may be referred to as a “transmitter” a “receiver,” or a“transceiver.” Further, in the following description, transmission andreception performed through the wireless channel may be used to have ameaning including the processing performed by the wireless communicationinterface 210 as described above.

The backhaul communication interface 220 provides an interface forperforming communication with other nodes within the network. That is,the backhaul communication interface 220 converts bitstreams transmittedto another node, for example, another access node, another BS, a highernode, or a core network, from the BS into a physical signal and convertsthe physical signal received from the other node into the bitstreams.

The storage unit 230 stores a basic program, an application, and datasuch as setting information for the operation of the BS 110. The storageunit 230 may include a volatile memory, a non-volatile memory, or acombination of volatile memory and non-volatile memory. Further, thestorage unit 230 provides stored data in response to a request from thecontroller 240.

The controller 240 controls the general operation of the BS. Forexample, the controller 240 transmits and receives a signal through thewireless communication interface 210 or the backhaul communicationinterface 220. Further, the controller 240 records data in the storageunit 230 and reads the recorded data. The controller 240 may performsfunctions of a protocol stack that is required from a communicationstandard. According to another implementation, the protocol stack may beincluded in the wireless communication interface 210. To this end, thecontroller 240 may include at least one processor. According to variousembodiments, the controller 240 may includes a command/code temporarilyresided in the controller 240, a storage space that stores thecommand/code, or a part of circuitry of the controller 240.

According to exemplary embodiments of the present disclosure, thecontroller 240 may configure a beam failure recovery configurationcomprising at least one reference signal for identifying a candidatebeam for the beam failure recovery and associated random access (RA)parameters, and transmit, to a terminal, the beam failure recoveryconfiguration for the beam failure recovery. For example, the controller240 may control the base station to perform operations according to theexemplary embodiments of the present disclosure.

FIG. 3 illustrates the terminal in the wireless communication systemaccording to various embodiments of the present disclosure. A structureexemplified at FIG. 3 may be understood as a structure of the terminal120 or the terminal 130. The term “-module”, “-unit” or “-er” usedhereinafter may refer to the unit for processing at least one functionor operation, and may be implemented in hardware, software, or acombination of hardware and software.

Referring to FIG. 3 , the terminal 120 includes a communicationinterface 310, a storage unit 320, and a controller 330.

The communication interface 310 performs functions fortransmitting/receiving a signal through a wireless channel. For example,the communication interface 310 performs a function of conversionbetween a baseband signal and bitstreams according to the physical layerstandard of the system. For example, in data transmission, thecommunication interface 310 generates complex symbols by encoding andmodulating transmission bitstreams. Also, in data reception, thecommunication interface 310 reconstructs reception bitstreams bydemodulating and decoding the baseband signal. In addition, thecommunication interface 310 up-converts the baseband signal into an RFband signal, transmits the converted signal through an antenna, and thendown-converts the RF band signal received through the antenna into thebaseband signal. For example, the communication interface 310 mayinclude a transmission filter, a reception filter, an amplifier, amixer, an oscillator, a DAC, and an ADC.

Further, the communication interface 310 may include a plurality oftransmission/reception paths. In addition, the communication interface310 may include at least one antenna array consisting of a plurality ofantenna elements. In the hardware side, the wireless communicationinterface 210 may include a digital circuit and an analog circuit (forexample, a radio frequency integrated circuit (RFIC)). The digitalcircuit and the analog circuit may be implemented as one package. Thedigital circuit may be implemented as at least one processor (e.g., aDSP). The communication interface 310 may include a plurality of RFchains. The communication interface 310 may perform beamforming.

The communication interface 310 transmits and receives the signal asdescribed above. Accordingly, the communication interface 310 may bereferred to as a “transmitter,” a “receiver,” or a “transceiver.”Further, in the following description, transmission and receptionperformed through the wireless channel is used to have a meaningincluding the processing performed by the communication interface 310 asdescribed above.

The storage unit 320 stores a basic program, an application, and datasuch as setting information for the operation of the terminal 120. Thestorage unit 320 may include a volatile memory, a non-volatile memory,or a combination of volatile memory and non-volatile memory. Further,the storage unit 320 provides stored data in response to a request fromthe controller 330.

The controller 330 controls the general operation of the terminal 120.For example, the controller 330 transmits and receives a signal throughthe communication interface 310. Further, the controller 330 recordsdata in the storage unit 320 and reads the recorded data. The controller330 may performs functions of a protocol stack that is required from acommunication standard. According to another implementation, theprotocol stack may be included in the communication interface 310. Tothis end, the controller 330 may include at least one processor ormicroprocessor, or may play the part of the processor. Further, the partof the communication interface 310 or the controller 330 may be referredto as a communication processor (CP). According to various embodiments,the controller 330 may includes a command/code temporarily resided inthe controller 330, a storage space that stores the command/code, or apart of circuitry of the controller 330.

According to exemplary embodiments of the present disclosure, thecontroller 330 may receive, from a base station (BS), a beam failurerecovery configuration comprising at least one reference signal foridentifying a candidate beam for the beam failure recovery andassociated random access (RA) parameters, identify the candidate beamfor the beam failure recovery using the at least one reference signal,and perform a physical random access channel (PRACH) using the at leastone reference signal and the associated RA parameters on the candidatebeam for the beam failure recovery. For example, the controller 330 maycontrol the terminal to perform operations according to the exemplaryembodiments of the present disclosure.

FIG. 4 illustrates the communication interface in the wirelesscommunication system according to various embodiments of the presentdisclosure. FIG. 4 shows an example for the detailed configuration ofthe communication interface 210 of FIG. 2 or the communication interface310 of FIG. 3 . More specifically, FIG. 4 shows elements for performingbeamforming as part of the communication interface 210 of FIG. 2 or thecommunication interface 310 of FIG. 3 .

Referring to FIG. 4 , the communication interface 210 or 310 includes anencoding and circuitry 402, a digital circuitry 404, a plurality oftransmission paths 406-1 to 406-N, and an analog circuitry 408.

The encoding and circuitry 402 performs channel encoding. For thechannel encoding, at least one of a low-density parity check (LDPC)code, a convolution code, and a polar code may be used. The encoding andcircuitry 402 generates modulation symbols by performing constellationmapping.

The digital circuitry 404 performs beamforming for a digital signal (forexample, modulation symbols). To this end, the digital circuitry 404multiples the modulation symbols by beamforming weighted values. Thebeamforming weighted values may be used for changing the size and phraseof the signal, and may be referred to as a “precoding matrix” or a“precoder.” The digital circuitry 404 outputs the digitally beamformedmodulation symbols to the plurality of transmission paths 406-1 to406-N. At this time, according to a multiple input multiple output(MIMO) transmission scheme, the modulation symbols may be multiplexed,or the same modulation symbols may be provided to the plurality oftransmission paths 406-1 to 406-N.

The plurality of transmission paths 406-1 to 406-N convert the digitallybeamformed digital signals into analog signals. To this end, each of theplurality of transmission paths 406-1 to 406-N may include an inversefast Fourier transform (IFFT) calculation unit, a cyclic prefix (CP)insertion unit, a DAC, and an up-conversion unit. The CP insertion unitis for an orthogonal frequency division multiplexing (OFDM) scheme, andmay be omitted when another physical layer scheme (for example, a filterbank multi-carrier: FBMC) is applied. That is, the plurality oftransmission paths 406-1 to 406-N provide independent signal processingprocesses for a plurality of streams generated through the digitalbeamforming. However, depending on the implementation, some of theelements of the plurality of transmission paths 406-1 to 406-N may beused in common.

The analog circuitry 408 performs beamforming for analog signals. Tothis end, the digital circuitry 404 multiples the analog signals bybeamforming weighted values. The beamformed weighted values are used forchanging the size and phrase of the signal. More specifically, accordingto a connection structure between the plurality of transmission paths406-1 to 406-N and antennas, the analog circuitry 408 may be configuredin various ways. For example, each of the plurality of transmissionpaths 406-1 to 406-N may be connected to one antenna array. In anotherexample, the plurality of transmission paths 406-1 to 406-N may beconnected to one antenna array. In still another example, the pluralityof transmission paths 406-1 to 406-N may be adaptively connected to oneantenna array, or may be connected to two or more antenna arrays.

Embodiments herein provide a method for handling a beam failure recoveryin a wireless communication system. The method includes configuring, bya BS, a beam failure recovery configuration include at least onereference signal for identifying a candidate beam for the beam failurerecovery and associated Random Access (RA) parameters. Further, themethod includes indicating, by the B S, the beam failure recoveryconfiguration to a UE for the beam failure recovery.

Embodiments herein provide a method for handling a beam failure recoveryin a wireless communication system. The method includes receiving, by aUE, a beam failure recovery configuration include at least one referencesignal for identifying a candidate beam for the beam failure recoveryand associated RA parameters from a BS. Further, the method includesidentifying, by the, UE a candidate beam for the beam failure recoveryusing the at least one reference signal. Furthermore, the methodincludes performing, by the UE, a PRACH using the at least one referencesignal and the associated RA parameters on the candidate beam for thebeam failure recovery.

Unlike conventional methods and systems, the proposed method can be usedfor handling the beam failure recovery using the PRACH. The proposedmethod allows the UE to send the PRACH for a beam failure recoveryrequest. Further, the proposed method can be used to detect whether abeam failure recovery response is received within a timer value and amaximum retransmission limit. Further, the proposed method can be usedto report a Radio Link Failure (RLF) to the BS, when the timer value andthe maximum retransmission limit is expired. This results in performingthe beam failure recovery in an enhanced manner.

The proposed method can be used to identify a candidate beam based onReference Signal Received Power (RSRP) measurement of plurality ofbeams. Further, the proposed method can select the beam as the candidatebeam when the beam reaches a threshold value in the RSRP measurement.Furthermore, the proposed method can perform the beam failure recoveryby sending the PRACH on the identified candidate beam.

Unlike conventional methods and systems, the proposed method allows theUE to perform the beam failure recovery by sending the PRACH using anarrow beam signal (e.g., CSI-RS), and wait for the beam failurerecovery response from the BS, until the timer value and the maximumretransmission limit is expired for the narrow beam signal. If the timervalue and the maximum retransmission limit has expired for the narrowbeam signal then, the UE can send the PRACH using a broad beam signal(e.g., SS block), and wait for the beam failure recovery response fromthe BS, until the timer value and the maximum retransmission limit isexpired for the broad beam signal. Further, the UE can report the RLF tothe BS in response to failure in receiving the beam failure recoveryresponse within the timer value and the maximum retransmission limit.

The proposed method herein is applicable for any future wirelesstechnologies that can be built upon beam-forming based systems. Itshould be noted that irrespective of the exact signals used i.e., SSblock and CSI-RS, the embodiments in the proposed method and system areapplicable for all cases where wide beams and/or narrow beams are used.

Referring now to the drawings, and more particularly to FIGS. 6 through17 , there are shown preferred embodiments.

FIG. 6 is a block diagram of a wireless communication system in which aBS 600 communicates with a UE 650, according to an embodiment asdisclosed herein. In an embodiment, the BS 600 includes a transceiver602, a beam failure recovery engine 604 includes a configurationindicator 606, a communicator 608, a processor 610, and a memory 612.The BS 600 can be for example but not limited to a next Generation NodeB(gNB), evolved NodeB (eNB), NR, and the like. The transceiver 602 can beconfigured to communicate with the UE 650 for performing a transmissionand reception of signals.

In an embodiment, the beam failure recovery engine 654 configures a beamfailure recovery configuration include at least one reference signal foridentifying a candidate beam for the beam failure recovery andassociated Random Access (RA) parameters. In an example, the at leastone reference signal is one of a Synchronization Signal (SS) block and aChannel State Information Reference Signal (CSI-RS), where the SS blockis a broad beam and the CSI-RS is a narrow beam.

In an embodiment, the beam failure recovery configuration is configuredfor any one of a Contention-Free Random Access Physical Random AccessChannel (CFRA PRACH) and a Contention-Based Random Access PhysicalRandom Access Channel PRACH (CBRA PRACH). In a contention-free proceduresuch as the CFRA PRACH, each UE 650 is given with dedicated resourcesfor sending a random access preamble to the BS 600. In acontention-based procedure such as the CBRA PRACH, the UE 650 needs tocontend with several other UEs in order to successfully connect with theBS 600.

In an embodiment, the associated RA parameters include a RACH preamble,RACH resources in a time domain and a frequency domain, a timer value, amaximum retransmission limit, a power ramping value and a Random AccessResponse (RAR) window response configuration and preamble indices.

The associated RA parameters such as the timer value, maximumretransmission limit for the beam failure recovery can be:

-   -   a) fixed in MAC specification/3GPP standard specification, or    -   b) indicated to the UE 650 using a Radio Resource Control (RRC)        signaling, a Downlink Control Indicator (DCI) and MAC Control        Element (MAC-CE) signaling.

In an embodiment, the configuration indicator 606 is configured toindicate the beam failure recovery configuration to the UE 650 for thebeam failure recovery. The configuration indicator 606 is configured toindicate the beam failure recovery configuration using at least one ofthe RRC signaling, a DCI and a MAC-CE signaling.

In an embodiment, the communicator 608 is configured to communicate withthe UE 650 and internally between hardware components in the BS 600. Inan embodiment, the processor 610 is configured to process variousinstructions stored in the memory 612 for handling the beam failurerecovery in the wireless communication system.

The memory 612 may include non-volatile storage elements. Examples ofsuch non-volatile storage elements may include magnetic hard discs,optical discs, floppy discs, flash memories, or forms of electricallyprogrammable memories (EPROM) or electrically erasable and programmable(EEPROM) memories. In addition, the memory 612 may, in some examples, beconsidered a non-transitory storage medium. The term “non-transitory”may indicate that the storage medium is not embodied in a carrier waveor a propagated signal. However, the term “non-transitory” should not beinterpreted that the memory 612 is non-movable. In some examples, thememory 612 can be configured to store larger amounts of information thanthe memory. In certain examples, a non-transitory storage medium maystore data that can, over time, change (e.g., in Random Access Memory(RAM) or cache).

In an embodiment, the UE 650 includes a transceiver 652, a beam failurerecovery engine 654 includes an association engine 656, a communicator658, a processor 660 and a memory 662. The transceiver 652 can beconfigured to communicate with the BS 600 for performing a transmissionand reception of signals.

The UE 650 can include, for e.g., a cellular telephone, a smartphone, apersonal computer (PC), a minicomputer, a desktop, a laptop, a handheldcomputer, Personal Digital Assistant (PDA), or the like. The UE 650 maysupport multiple Radio access technologies (RAT) such as, for e.g.,Code-division multiple access (CDMA), General Packet Radio Service(GPRS), Evolution-Data Optimized EVDO (EvDO), Time-division multipleaccess (TDMA), GSM (Global System for Mobile Communications, WiMAX(Worldwide Interoperability for Microwave Access) technology, LTE, LTEAdvanced and 5G communication technologies.

In an embodiment, the beam failure recovery engine 654 is configured toreceive the beam failure recovery configuration include the at least onereference signal for identifying the candidate beam for the beam failurerecovery and associated RA parameters from the BS 600.

In an embodiment, beam failure recovery configuration include at leastone reference signal for identifying the candidate beam for the beamfailure recovery and associated Random Access (RA) parameters. Theassociated RA parameters include a RACH preamble, RACH resources in atime domain and a frequency domain, a timer value, a maximumretransmission limit, a power ramping value and a Random Access Response(RAR) window response configuration and preamble indices.

In an embodiment, the RACH resources includes a SS block resource and aCSI-RS Resource. The SS block-resource includes SS block-Index and aRACH preamble Index. The SS block-Index is used by the UE 650 to performthe beam failure recovery upon identifying the candidate beam from thereference signal (e.g., SS block) and the RACH preamble index is aninteger value.

The CSI-RS Resource includes a CSI-RS Index and Non-Zero-Power(NZP)-CSI-RS-Resource Id and the RACH preamble Index. TheNZP-CSI-RS-Resource Id indicate RA occasions that the UE 650 can useduring the beam failure recovery, upon selecting the candidate beamidentified by this CSI-RS.

If a field (such as NZP-CSI-RS-Resource Id) is not available in the beamfailure configuration then, the UE 650 can use the RA occasionassociated with the SS block that is Quasi Co-Location (QCL) with theCSI-RS. Further, the UE 650 can use the preamble index for the RAoccasions associated with the CSI-RS. If the preamble indices is notavailable in the beam failure configuration, the UE 650 uses thepreamble index associated with the SS block that is in QCL relationshipwith the CSI-RS.

In an embodiment, the candidate beam identifier 656 is configured toidentify the candidate beam for the beam failure recovery using the atleast one reference signal. The candidate beam identifier 656 identifiesthe candidate beam based on a Reference Signal Received Power (RSRP)threshold configured for the beam failure recovery.

In an embodiment, a Layer 1 (L1)-RSRP threshold can used for determiningwhether the candidate beam can be used by the UE 650 to attemptcontention-free PRACH. The list of reference signals (such as CSI-RSand/or SSB) identifies the candidate beams for the beam failurerecovery.

Further, the beam failure recovery engine 654 is configured to perform aPRACH using the at least one reference signal and the associated RAparameters on the candidate beam for the beam failure recovery. In anexample, the PRACH is one of a Contention-Free Random Access PhysicalRandom Access Channel (CFRA PRACH) and a Contention-Based Random AccessPhysical Random Access Channel PRACH (CBRA PRACH).

In an embodiment, the beam failure recovery engine 654 is configured todetermine whether the CFRA PRACH or the CBRA PRACH to be based on theassociated RA parameters configured to the UE 650 on the candidate beamfor the beam failure recovery.

In an embodiment, the beam failure recovery engine 654 is configured toperform the CFRA PRACH using the SS block as the reference signal andthe associated RA parameters on the candidate beam for the beam failurerecovery.

In another embodiment, the beam failure recovery engine 654 isconfigured to perform the CFRA PRACH using the CSI-RS as the referencesignal and the associated RA parameters on the candidate beam for thebeam failure recovery.

In yet another embodiment, the beam failure recovery engine 654 isconfigured to perform the CFRA PRACH using the CSI-RS as the referencesignal and the associated RA parameters on the candidate beam for thebeam failure recovery and then by using the SS block as the referencesignal and the associated RA parameters on the candidate beam for thebeam failure recovery.

The RAR window starts immediately after the PRACH (i.e., Msg1)transmission. The BS 600 configures a length of the RAR window as “X”symbols/slot. The BS 600 can configure the UE 650 to send multiple Msg1for the beam failure recovery purposes. Further, the UE 650 can transmitmultiple Msg1 for the beam failure recovery, when the multiple candidatebeams are identified.

In an embodiment, the beam failure recovery engine 654 is configured toperform the CBRA PRACH is performed using the SS block as the referencesignal and the associated RA parameters on the candidate beam for beamfailure recovery.

In an embodiment, the beam failure recovery engine 654 is configured todetect whether the beam failure recovery response is received from theBS 600. In an embodiment, the beam failure is detected by lower layersand indicated to the MAC entity. The MAC entity perform the following:

-   -   1. if the beam failure indication has been received from the        lower layers:    -   a. Start beam Failure Recovery Timer; and    -   b. Initiate a Random Access procedure on the Primary Secondary        cell (SpCell).    -   2. If the beam Failure Recovery Timer expires:    -   a. Indicate a failure of a beam failure recovery request to        higher layers.

In an embodiment, the beam failure recovery engine 654 is configured toidentify whether other candidate beam for the beam failure recovery isavailable. Further, the beam failure recovery engine 654 is configuredto determine whether the timer value has expired for performing the beamfailure recovery or the maximum retransmission limit for sending thePRACH for the beam failure recovery is met based on the indication ofassociated RA parameters.

In an embodiment, two counters such as a PREAMBLE_TRANSMISSION_COUNTERfor the beam failure recovery and a PREAMBLE_POWER_RAMPING_COUNTER forthe beam failure recovery are defined in the MAC specification. The MACentity initializes PREAMBLE_TRANSMISSION_COUNTER for beam failurerecovery and PREAMBLE_POWER_RAMPING_COUNTER for beam failure recovery to1, when the random access procedure is initiated. Further, the MACentity increments the PREAMBLE_TRANSMISSION_COUNTER for the beam failurerecovery by 1, when the RAR reception is not successful or contentionresolution is not successful. The MAC entity increments thePREAMBLE_POWER_RAMPING_COUNTER for beam failure recovery by 1, when theUE 650 does not change the beam during PRACH retransmission for the caseof beam failure recovery. The multiple Msg1 can overlap inside the beamrecovery response window.

Further, the beam failure recovery engine 654 is configured to performthe PRACH using reference signal and the associated RA parameters on theother candidate beam for the beam failure recovery when the timer valueis not expired or the maximum retransmission limit for sending the PRACHfor the beam failure recovery is not met.

In an embodiment, the beam failure recovery engine 654 is configured todetermine whether the CFRA PRACH or the CBRA PRACH to be performed basedon the associated RA parameters configured to the UE 650 on the othercandidate beam for the beam failure recovery.

In an embodiment, the beam failure recovery engine 654 is configured toperform the CFRA PRACH using the SS block as the reference signal andthe associated RA parameters on the other candidate beam for the beamfailure recovery.

In another embodiment, the beam failure recovery engine 654 isconfigured to perform the CFRA PRACH using the CSI-RS as the referencesignal and the associated RA parameters on the other candidate beam forthe beam failure recovery.

In yet another embodiment, the beam failure recovery engine 654 isconfigured to perform the CFRA PRACH using the CSI-RS as the referencesignal and the associated RA parameters on the other candidate beam forthe beam failure recovery and then by using the SS block as thereference signal and the associated RA parameters on the other candidatebeam for the beam failure recovery.

In an embodiment, the beam failure recovery engine 654 is configured toperform the CBRA PRACH is performed using the SS block as the referencesignal and the associated RA parameters on the other candidate beam forbeam failure recovery.

If the timer value is expired or the maximum retransmission limit forsending the PRACH is expired then, the beam failure recovery engine 654is configured to trigger a Radio Link Failure (RLF) to the BS 600.

In an embodiment, the communicator 658 is configured to communicate withthe UE 650 and internally between hardware components in the BS 600. Inan embodiment, the processor 660 is configured to process variousinstructions stored in the memory 662 for handling the beam failurerecovery in the wireless communication system.

The memory 662 may include non-volatile storage elements. Examples ofsuch non-volatile storage elements may include magnetic hard discs,optical discs, floppy discs, flash memories, or forms of electricallyprogrammable memories (EPROM) or electrically erasable and programmable(EEPROM) memories. In addition, the memory 662 may, in some examples, beconsidered a non-transitory storage medium. The term “non-transitory”may indicate that the storage medium is not embodied in a carrier waveor a propagated signal. However, the term “non-transitory” should not beinterpreted that the memory 662 is non-movable. In some examples, thememory 662 can be configured to store larger amounts of information thanthe memory. In certain examples, a non-transitory storage medium maystore data that can, over time, change (e.g., in Random Access Memory(RAM) or cache).

In an embodiment, consider the UE 650 is configured to send the PRACH(i.e., Msg1) on the candidate beam (e.g., CSI-RS). The UE 650 waits fora recovery response in the RAR window. Further, if a positive response(i.e., recovery response) is received from the BS 600 then, a beamfailure recovery procedure is ended. Otherwise, the UE 650 can searchfor more candidate beams for the beam failure recovery. Furthermore, ifthere is an expiry of the timer value or the maximum retransmissionlimit expired, then the UE 650 is configured to trigger the RLF tohigher layers. In an example, the medium access control (MAC) layer isthe higher layer and the lower layer can be physical layer and the datalink layer of a protocol stack.

Although the FIG. 6 shows various hardware components of the BS 600 andthe UE 650 but it is to be understood that other embodiments are notlimited thereon. In other embodiments, the BS 600 and the UE 650 mayinclude less or more number of components. Further, the labels or namesof the components are used only for illustrative purpose and does notlimit the scope of the invention. One or more components can be combinedtogether to perform same or substantially similar function of handlingthe beam failure recovery in the wireless communication system.

Further, some new requirements from NR also make non-contention basedrandom access inefficient. To maintain high data rate, fast hand-over isessential with stringent delay constraint. However, due to the densityof the PRACH might be low, using those PRACH may not be enough whichwould lead to large delay, which cannot fulfill the delay requirementfor fast hand-over. Further, CSI-RS based RACH procedure has been agreedfor the case of handover purposes. Here we discuss the feasibility ofperforming RACH procedure based on CSI-RS for the case of beam recovery.As a baseline, CSI-RS has been agreed to be sued for the beam recoveryprocedure. This includes all steps in beam recovery starting fromidentification of beam failure and sending a recovery request. Thisrecovery request can be sent via a PRACH. The traditionalcontention-free RACH mechanism is sufficient to support this beamrecovery procedure and a 4-step RACH procedure is not necessary (as theUE context exists with the network and beam recovery is entirely an L1procedure). Further, Ran1 agreed to support carriers without SS blocks.In such carriers, to support beam management CSI-RS must be configured.In such cases, the beam recovery procedure can be supported only viaCSI-RS. Hence, the necessary PRACH procedure for the same must besupported via CSI-RS.

Further, the difference between handover and beam recovery is that beamrecovery is a random event and recovery resources cannot be configuredfor the same after receiving a request as it may increase the delay inthe recovery procedure. Hence, if PRACH is supported as the recoverymechanism the resources and/or preambles for the same may be defined ina dedicated manner. If the resources are shared with initial accessRACH, then dedicated preambles for the purpose of beam recovery may bedefined. A dedicated preamble for the same may be given to the UE atconnection setup phase. However, if the preambles are limited, then thePRACH resources must be defined in a dedicated manner only for thispurpose. These resources can be FDM or TDM. Performance of CDM-basedmechanisms highly depends on the channel conditions and may loseorthogonality in extreme Doppler and fading conditions. Further, inorder to avoid additional signaling of the time location of theseresources, the network may choose to define these in an FDM manner withthe initial access RACH resources. Since the available RACH preamblesare already limited and may not be extended at least in the Phase-1 ofNR, it is preferred to define dedicated PRACH resources for the case ofbeam recovery.

The retransmission behavior for this RACH procedure is same as thecontention free RACH procedure. A configurable number of PRACH attemptswill be made by the UE, as agreed in the last meeting, and beyond thisthe UE may indicate to the higher layers about such a failure. A maximumretransmission limit for the case of beam failure recovery may beindicated to the UE which may or may not be different from the initialaccess RACH. This limit may be indicated to the UE at the connectionsetup phase as it is not needed before this procedure. If gNB configuresSS block for beam recovery, then RACH based on same can be used. If noneof the contention-free RACH resources are configured for beam recoverypurposes, then contention-based RACH whenever it is available for UE canbe used i.e., the earliest RACH configuration indicates the slot/symbolwhere RACH resources are available can be used. Some t/f resources forthe recovery purposes and then map the CSI-RS/SS to these resources aredesigned. Further, the total number of resources will depend on the gNBimplementation. Further, dedicated preambles to UE at RRC CONN stage isgiven. Then for each CSI-RS/SS, some FDM of resources which differentUEs can choose randomly to minimize collisions are defined.

FIG. 7 is a sequence diagram illustrating various signaling messagescommunicated between the BS 600 and the UE 650 for handling the beamfailure recovery in the wireless communication system, according to anembodiment as disclosed herein.

At step 702, the UE 650 establishes a radio resource control (RRC)connection with the BS 600. At step 704, the BS 600 can configure thereference signal and the associated RA parameters. The BS 600 configuresthe beam to the UE 650 for receiving the PDCCH, where the beam isindicated using one of:

-   -   a. Explicitly configuring one Periodic CSI-RS (P-CSI-RS) or SS        block, where P is the period of a CSI-RS transmission    -   b. Implicitly configuring the P-CSI-RS or SS block associated        with the Target Cell Identity (TCI) configured to one PDCCH.

In one embodiment, the BS may transmit the reference signal to the UEaccording to a period and a slot offset which are configured in resourcefor the reference signal. For example, the BS may transmit the CSI-RS tothe UE according to a period and a slot offset which are configured inresource for the CSI-RS.

At step 706, the UE 650 detects that there exist the beam failure (e.g.,object blockage) based on a failure of decoding the PDCCH associatedwith the beam. The beam failure condition is determined based on BlockError Rate (BLER) on the PDCCH, where the BLER is a ratio of the numberof erroneous blocks to the total number of blocks transmitted. The UE650 detects that the consecutive number of PDCCH is failed then the UE650 detects that there is the beam failure.

At step 708, the UE 650 identifies the candidate beam based on thereference signal. The candidate beam is identified based on the RSRPmeasurement on the reference signal. Further, at step 710, the UE 650 isconfigured to perform the beam failure recovery request using the PRACHon the identified candidate beam. The UE 650 can send the beam recoveryrequest via the PRACH, only if the number of consecutive detected beamfailure instance exceeds a configured maximum number. In one embodiment,sending the beam recovery request via the PRACH comprises transmitting arandom access preamble for the beam failure recovery. In one embodiment,the candidate beam may include a beam for uplink or downlink. Also, thecandidate beam may be a beam that is not used for data communication butis good enough to allow data communication. When the UE identifies thecandidate beam based on the reference signal, the UE may report N beamsof good quality to the BS. And, the BS may select most appropriate beamamong the N beams and transmit the most appropriate beam to the UE.Then, the UE may use the most appropriate beam for data communication.The remaining N−1 beams may be candidate beams.

At step 712, the UE 650 is configured to monitor the beam failurerecovery response for the PRACH, from the BS 600. If the UE 650 receivesthe beam failure recovery response with the RAR window specified in theRA parameters then, the UE 650 considers that the recovery responsereception is successful and stops a beam failure recovery procedure.

If the UE 650 does not receive the beam failure recovery response withinthe RAR window, the UE 650 can retransmit the PRACH on the othercandidate beam and wait for the timer value. Further, if the UE 650 doesnot receive the recovery response after the maximum number ofretransmission of PRACH, the UE 650 can report the beam failure to theBS 600. Further, the beam failure is determined when all serving beams(e.g., SS block, CSI-RS) fails. The UE 650 can report the beam failureto the higher layers. In one embodiment, the number of retransmission ofPRACH is transmitted to the UE through a RRC parameter (i.e. the RRAparameter).

FIGS. 8A and 8B are flow diagrams illustrating various operations forhandling the beam failure recovery in the wireless communication system,according to an embodiment as disclosed herein. The flow diagrams fromFIG. 8A to FIG. 8B are connected as a flow diagram 800.

At 802, the method includes configuring, by the BS 600, the beam failurerecovery configuration include at least one reference signal foridentifying the candidate beam for the beam failure recovery andassociated RA parameters. In an embodiment, the method allows the beamfailure recovery engine 604 to configure the beam failure recoveryconfiguration include at least one reference signal for identifying thecandidate beam for the beam failure recovery and associated RAparameters.

At 804, the method includes indicating, by the BS 600, the beam failurerecovery configuration to the UE 650 for the beam failure recovery. Inan embodiment, the method allows the configuration indicator 606 toindicate the beam failure recovery configuration to the UE 650 for thebeam failure recovery.

At 806, the method includes receiving, by the UE 650, the beam failurerecovery configuration includes the at least one reference signal foridentifying the candidate beam for the beam failure recovery andassociated RA parameters from the BS 600. In an embodiment, the methodallows the beam failure recovery engine 654 to receive the beam failurerecovery configuration.

At 808, the method includes identifying, by the UE 650, the candidatebeam for the beam failure recovery using the at least one referencesignal. In an embodiment, the method allows the candidate beamidentifier 656 to identify the candidate beam for the beam failurerecovery using the at least one reference signal.

At 810, the method includes performing, by the UE 650, the PRACH usingthe at least one reference signal and the associated RA parameters onthe candidate beam for the beam failure recovery. In an embodiment, themethod allows the beam failure recovery engine 654 to perform the PRACHusing the at least one reference signal and the associated RA parameterson the candidate beam for the beam failure recovery.

At 812, the method includes detecting, by the UE 650, whether the beamfailure recovery response is received from the BS 600. In an embodiment,the method allows the beam failure recovery engine 654 to detect whetherthe beam failure recovery response is received from the BS 600. In oneembodiment, the UE may hear for BS response within RAR window. If thereis no response detected by the UE within the RAR window, the UE mayperform retransmission of the request. If the response is not detectedafter a certain number of transmission(s) for beam failure recoveryrequests (either RACH or PUCCH), UE may notify higher layer entities,and stop from further beam failure recovery.

At 814, the method includes identifying, by the UE 650, whether othercandidate beam for the beam failure recovery is available. In anembodiment, the method allows the beam failure recovery engine 654 toidentify whether other candidate beam for the beam failure recovery isavailable. In one embodiment, if no candidate beam is known to UE forrecovery request, then UE may send RLF (i.e. trigger RLF).

At 816, the method includes determining, by the UE 650, whether thetimer value is expired for the beam failure recovery or the maximumretransmission limit for sending the PRACH for the beam failure recoveryis met. In an embodiment, the method allows the beam failure recoveryengine 654 to determine whether the timer value is expired for the beamfailure recovery or the maximum retransmission limit for sending thePRACH for the beam failure recovery is met.

If the timer value is expired for the beam failure recovery or themaximum retransmission limit for sending the PRACH for the beam failurerecovery is met then, at 818, the method includes triggering, by the UE650, the Radio Link Failure (RLF). In an embodiment, the method allowsthe beam failure recovery engine 654 to trigger the RLF to the BS 600.In one embodiment, the timer expires, and reaching the retransmissionlimit may indicate the beam failure recovery has failed. So, the RLF istriggered.

If the timer value is not expired for the beam failure recovery or themaximum retransmission limit for sending the PRACH for the beam failurerecovery is not met then, at 820, the method includes performing, by theUE 650, the PRACH using reference signal and the associated RAparameters on the other candidate beam for the beam failure recovery. Inan embodiment, the method allows the beam failure recovery engine 654 toperform the PRACH using reference signal and the associated RAparameters on the other candidate beam for the beam failure recovery.

The various actions, acts, blocks, steps, or the like in the flowdiagram 800 may be performed in the order presented, in a differentorder or simultaneously. Further, in some embodiments, some of theactions, acts, blocks, steps, or the like may be omitted, added,modified, skipped, or the like without departing from the scope of theinvention.

FIG. 9 is a flow diagram 900 illustrating various operations performedby the UE 650 for sending the PRACH for the beam failure recovery,according to an embodiment as disclosed herein.

At 902, the method includes identifying, by the UE 650, the beam failureon the wireless communication system. In an embodiment, the methodallows the beam failure recovery engine 654 to identify the beam failureon the wireless communication system.

At 904, the method includes triggering, by the UE 650, the beam failurerecovery using the PRACH. In an embodiment, the method allows the beamfailure recovery engine 654 to trigger the beam failure recovery usingthe PRACH.

At 906, the method includes performing, by the UE 650, the PRACH usingthe CSI-RS as the reference signal until the timer value (T1) expiresand the maximum retransmission limit (N1) is met. In an embodiment, themethod allows the beam failure recovery engine 654 to perform the PRACHusing the CSI-RS as the reference signal until the timer value (T1)expires and the maximum retransmission limit (N1) is met. In oneembodiment, the RAR window may be set by considering the timer value(T1) and the maximum retransmission limit (N1) for the CSI-RS. And, theRAR window may be indicated to the UE 650.

Further, the UE 650 waits for the recovery response from the BS 600. Ifthere is no recovery response detected by the UE 650 within the RARwindow then, at 908, the method includes performing, by the UE 650, thePRACH using the SS block as the reference signal until the timer value(T2) expires and the maximum retransmission limit (N2) is met. In anembodiment, the method allows the beam failure recovery engine 654 toperform the PRACH using the SS block as the reference signal until thetimer value (T2) expires and the maximum retransmission limit (N2) ismet. In one embodiment, the performing the PRACH using the SS block mayindicate that a signal which is spatial QCL (quasi-co-located) is set asthe SS block.

At 910, the method includes triggering, by the UE 650, the RLF when thetimer value (T2) expires and the maximum retransmission limit (N2)expires. In an embodiment, the method allows the beam failure recoveryengine 654 to trigger the RLF when the timer value (T2) expires and themaximum retransmission limit (N2) expires.

In an embodiment, based on the network configuration, RA parameters suchas T1, N1 can be defined with respect to CSI-RS and the parameters suchas T2, N2 can be defined with respect to SS block. Further, these RAparameters are indicated to the UE 650 in a specific manner during a RRCconnection setup.

In an embodiment, for beam failure recovery, similar to RAR window, a“beam recovery window” is defined. The UE hears for gNB response withinthis time window. If there is no response detected by the UE within thewindow, the UE may perform retransmission of the request. If theresponse is not detected after a certain number of transmission(s) forbeam failure recovery requests (either RACH or PUCCH), UE notifieshigher layer entities, and stops from further beam failure recovery.

The various actions, acts, blocks, steps, or the like in the flowdiagram 900 may be performed in the order presented, in a differentorder or simultaneously. Further, in some embodiments, some of theactions, acts, blocks, steps, or the like may be omitted, added,modified, skipped, or the like without departing from the scope of theinvention.

FIGS. 10A-10C are illustrating a scenario in which the recovery responseis received from the BS 600 for the beam failure recovery, according toan embodiment as disclosed herein.

In an embodiment, when the UE 650 receives the recovery response fromthe BS 600 in response to the transmission of PRACH (e.g., Msg1) then,the UE 650 considers that the recovery response is successful and stopsmonitoring further responses and stops the beam recovery procedures.

As shown in the FIG. 10A, a single recovery response window exists tocover all Msg1, in which the UE 650 can monitor the recovery responseafter Msg1 transmission. As shown in the FIG. 10B, the single recoveryresponse window recovers response monitoring after all ‘n’ Msg1transmissions. The set of Msg1 transmissions are performed by the UE 650within the timer value (T1) and further the recovery response isreceived by the UE 650 from the BS 600 after the ‘n’ Msg1 transmissionswith the timer value (T1). As shown in the FIG. 10C, a multiple recoveryresponse windows for each Msg1 is available for recovery responsemonitoring after each Msg1 transmission. In the FIGS. 10A-10C, the ‘T’means a duration of the RACH occasion.

The BS 600 can configure the UE 650 to use any one of the RAR windowconfiguration as shown in the FIGS. 10A-10C, in order to supportmultiple Msg1 for the purpose of beam failure recovery. The multiplerecovery responses can be multiplexed within one Media Access ControlProtocol Data Unit (MAC PDU) corresponding to beam failure recoveryresponse. The MAC PDU comprises the following:

-   -   a. MAC Header+zero or more MAC beam recovery responses+padding        (optional);    -   b. One or more MAC sub-PDUs+padding (optional), in which each        MAC sub-PDU has independently the beam recovery response.

In an embodiment, each MAC sub-PDU includes one of the following:

-   -   a. a MAC sub-header only (or)    -   b. a MAC sub header and a MAC RAR.

The power ramping rules in the various embodiments of the presentdisclosure is described below. The power ramping rules for the beamrecovery is same as for initial access RACH. Maintain same counters forthe case of beam switching, Increment for every failure. If the UEconducts beam switching, the counter of power ramping remains unchanged.The UE calculates the PRACH transmit power for the retransmission ofbeam recovery if it is possible at least based on the most recentestimate path loss and power ramping. The path loss is measured at leaston the CSI-RS associated or on the QCL'ed SS block associated with thePRACH resources/preamble subset for the case where beam recovery Msg1 issent. When UE reaching the maximum power, If the recalculated power isstill at or above the Pc, max, the UE can transmit at maximum power evenif it changes its TX beam. This Pc, max can be different from initialaccess since RACH is sent on CSI-RS (or SS) and higher limit may beallowed for faster beam recovery.

The cyclic shift configuration for beam recovery preamble formats in thevarious embodiments of the present disclosure is described below. Forthe case of initial access UL synch does not exist and N_(cs) must beprovisioned so as to cover for the ZCZ of the preamble sequence design.It also accommodates for restricted set design such as the high mobilitycases. However, this design can be more flexible in case of beamrecovery since UL synch already exists for the UEs.

-   -   Smaller N_(cs) values configured for the case of beam recovery        compared to initial access;    -   N_(cs) value explicitly indicated to UEs for the case of beam        recovery and for a specific preamble formats by the gNB at RRC        connection phase;    -   N_(cs) value also takes into account the UL TA values for        various beams and various UEs as TA values may change across        beams;    -   N_(cs) value adjusted by UE based on the corresponding TA value,        where base N_(cs) value is indicated to UE by gNB;    -   Different restricted sets to be used for the case of beam        recovery and indicated to UE via RRC signaling.

FIG. 11 is a schematic diagram illustrating multiple preamble formatsfor short sequence length according to various embodiments of thepresent disclosure. According to FIG. 11 , for 1 symbol PRACH preambleformat, multiple preamble formats can be sent anywhere inside slot andno issues whether slot=7/14 symbols while avoiding symbols needed forPDCCH scheduling and PUCCH scheduling to avoid interference. Similar toSS block mapping, leave symbols for PDCCH, PUCCH and then transmit Msg1.Further, for 2 symbol PRACH preamble format, PDCCH only supported, thenallowed RACH symbols are {2, 3}, {4, 5}, {6, 7}, {10, 11}, {12, 13}. TheGT between symbol index 7 and 8 should be considered. (support formatB). In format A, there is no GT in that format. So, gNB cannot receiveRACH during the period that PDCCH transmits on symbol 8 since RACH isreceived with round trip delay at gNB. That is, format B having smallnumber of RACH symbols should be considered in your scenario. Further,in case of 1-symbol PDCCH, allowed RACH symbols are {1, 2}, {3, 4}, {5,6}, {9, 10}, {11, 12} within a 14 symbol or 7 symbol slot, accordingly.

For 4-symbol PRACH preamble format,

-   -   For 1 symbol PDCCH, {1, 2, 3, 4} or {2, 3, 4, 5} or {3, 4, 5, 6}        or {4, 5, 6, 7} and same for 2^(nd) slot;    -   For 2-symbol PDCCH, {2, 3, 4, 5} or {3, 4, 5, 6} or {4, 5, 6, 7}        and same for second slot;    -   For 3-symbol PDCCH, {3, 4, 5, 6} or {4, 5, 6, 7} and same for        second slot;    -   Between symbol index 7 and 8, GT should be considered. (support        format B).

For 6-symbol PRACH preamble format,

-   -   For 1 symbol PDCCH, {1, 2, 3, 4, 5, 6} or {2, 3, 4, 5, 6, 7} and        same for 2^(nd) slot;    -   For {1, 2, 3, 4, 5, 6}, both format A and B can be supported.        Only format B is supported for {2, 3, 4, 5, 6, 7}.

For 12 symbol PRACH preamble format does not support for 7-symbol slot.A cross-slot transmission should be supported. If 7-symbol slot issupported, then 12-symbol RACH can cause complications and allowcross-slot transmissions and should avoid PDCCH in 2^(nd) slot. Becausecross-slot transmission in UL may not allow for gNB to schedule PDCCH inthe 2^(nd) slot (of 7 symbols). FIG. 11 shows multiple preamble formatsin 14-symbol slot. In this figure, two symbols from the beginning ofslot are assumed for PDCCH and Guard interval. Format C was introducedto enhance coverage enhancement to format A. From the coverage aspectbetween format A0 and C0, C0 provides better coverage, but the durationof C0 and C1 cannot be aligned with data channel due to their symboldurations (1.5 symbol/2.5 symbol). Further, when it is assumed first twosymbols are not used for RACH transmission, format A3 might be allocatedacross slots. And gNB cannot be allocated consecutive two A3 formatseven in 14-symbol slot. When we use format A3, there are three usagecase considering 7-symbol slot and 14-symbol slot, as represented inFIG. 3 . Considering UL/DL configuration, the RACH transmission shouldbe done within 7-symbol slot or 14-symbol slot.

FIG. 12 is a schematic diagram illustrating format A and C according tovarious embodiments of the present disclosure. According to FIG. 12 ,Format C was introduced to enhance coverage enhancement to format A.Further, FIG. 12 shows a detailed example when two consecutive preambleoccasions are configured. Further, when gNB perform FFT to second datasymbol, format C0 interferes with data. For the case that gNB performsFFT to 3^(rd) symbol, ICI happened due to format C1. The advantage offormat C compared to format A is to enhance coverage, but wide coveragecould be provided from other preamble formats. From the smallsupportable number of preamble format perspective, format C is notpreferred for preamble formats.

FIG. 13 is a schematic diagram illustrating three different allocationswhen format A3 is required according to various embodiments of thepresent disclosure; According to FIG. 13 , when format A3, there arethree usage cases considering 7-symbol slot and 14-symbol slot.Considering UL/DL configuration, the RACH transmission should be donewithin 7-symbol slot or 14-symbol slot. Figure (a) shows the PRACHmapping within 7-symbol slot. Format A3 within 7-symbol slot should beallocated at the first symbol as the last OFDM symbol can be used as GTto avoid ISI to following data channel. Figure (b) and (c) show caseswhen two preamble format occasions are considered during 14-symbol slot.Preamble format should be aligned with symbol inside 7 or 14-symbol slotand should avoid cross-slot transmissions.

FIG. 14 is a schematic diagram illustrating RACH preamble formataccording to presence of GT according to various embodiments of thepresent disclosure; According to FIG. 14 , two preamble formattransmissions are present based on format ‘A’ and format ‘B’. The usageof format B is to avoid ISI to following data symbol as GT is located atthe end of preamble format.

FIG. 15 is a schematic diagram illustrating usage scenarios for variousformats (A and B) according to various embodiments of the presentdisclosure. According to FIG. 15 , format A, TRP is used for beamcorrespondence and for format B, TRP does not have beam correspondence.When two preamble formats are configured, the GT between two preambleformat B may harm to data channel decoding. Therefore, it is preferableto locate format B at the end of slot. For the format A, when gNBscheduled data after RACH occasion, one-symbol guard interval betweendata and format A should be supported. Meanwhile, for the period thattwo PRACH formats are received, the last RACH occasion can be allocatedfor format B or one symbol-length guard interval can be inserted.

Further, a preamble based on format B is located at the end of the 7/14symbol slot and avoid any resource wastage due to GT insertion. Further,mapping of multiple PRACH preamble formats depends on the number ofPDCCH symbols. Further, 1 symbol duration preamble format, A0/B0

Format A0 and B0 are exactly same. Therefore, format B0 is to beremoved. Format A0 can be sent anywhere inside slot and there will be noissues whether a slot is 7/14 symbols while avoiding symbols needed forPDCCH scheduling. For 1 symbol preamble format, using format A0 issufficient.

-   -   2 symbol duration preamble format, A1/B1    -   As we discussed earlier, allocating format B at the end of slot        is preferred to avoid resource wastage, we don't see the usage        scenario for using format B1. For 2 symbol preamble format,        using format A1 is sufficient.    -   4 symbol duration preamble format, A2/B2    -   Format A2 is already agreed. Below table shows the candidate        PRACH symbol mapping in a slot:

Possible symbol mappings No 1 symbol 2 symbol 3 symbol Slot type PDCCHPDCCH PDCCH PDCCH 7 symbol No issue {2, 3, 4, 5}, {3, 4, 5, 6}* No roomslot {3, 4, 5, 6}* {10, 11, 12, 13}* {9, 10, 11, 12}, {10, 11, 12, 13}*14 symbol No issue No issue No issue No issue slot

For mapping of Format B, in 14 symbol slot, format A and B can besupported while avoiding symbols need for PDCCH scheduling or guardinterval. In 7 symbol slot, format A can support only the case that 1symbol PDCCH is scheduling. When format B, 1 or 2 symbol is used, PDCCHscheduling can be supported. Although using format B2 may provide moreTRP scheduling flexibility, the advantage seems not significant. Whenformat A2 is allocated at the beginning of slot, it can act like B2 withmore GT. Further, a 6-symbol duration preamble format, A3/B3, format Ais allocated at the beginning of a slot when 7-symbol slot isconfigured. In 14-symbol slot, format A can be allocated at thefirst/second symbol index. Similar to t-symbol duration preamble formatcase, format A can act like format B according to its allocation.

FIG. 16 is a schematic diagram illustrating RACH mapping according tovarious embodiments of the present disclosure. According to FIG. 16 ,the gNB can configure the UE about the RACH occasions based on the PDCCHdurations. gNB can dynamically indicate this RACH configuration. gNBindicates which format to use where A and B or A with guard period or Awith C or C alone etc. This signaling can be done via RACHconfiguration. Similar to mapping of the SS blocks based on SCS, RACHmapping can be done based on the sub-carrier spacing for the RACH whileavoiding the PDCCH duration. Further, sub-frame index etc. must beindicated in terms of the reference SS block numerology. Then dependingon indication and preamble format, the UE will adjust accordingly to fitwithin the subframe.

FIG. 17 is a schematic diagram illustrating various kinds of RACHmapping according to various embodiments of the present disclosure.According to FIG. 17 , distributed mapping may be better for latencysensitive applications. In this, mapping pattern depends on parametersin RACH configuration. In RACH configuration, the subframe index may beinformed in a frame. Both localized and distributed mapping can beutilized depends on parameters. Further, distributed mapping can be goodfor beam correspondence based devices. For BC devices, they only need tosend one RACH preamble. Then they may also receive RAR immediately ifthe adjacent symbols are not reserved for the case of RA-Ptransmissions. Further, localized mapping is good for no beamcorrespondence devices. For no BC cases, they need beam sweep. So, it isbetter if beam sweep is performed consecutively and by; one-shot(one-shot beam sweeping of “N” beams over “N” consecutive symbols); thenRAR window can start immediately at the end of the “N” symbols.Otherwise in case of distributed mapping, the UE will have to wait along time for sending the RACH on the N^(th) beam. This can cause accesslatency issues. Further, semi-localized can be good for partial beamcorrespondence devices. Semi-localized can be good for partial beamcorrespondence devices which is most likely the case of most userdevices.

For 15 kHz subcarrier spacing, the first OFDM symbols of the candidateRACH symbols in time domain have the OFDM symbol indices {2, 8}+14*nwithin the half frame which may contain RACH resources. For carrierfrequencies smaller than or equal to 3 GHz, n=0, 1. For carrierfrequencies larger than 3 GHz and smaller than or equal to 6 GHz, n=0,1, 2, 3. The number of RACH resources mapping depends on the SS blocksmapping. This can be done exactly for 1-1 mapping between SS blocks andRACH resources. If this 1-1 mapping cannot be done, then some of thesesymbols can be left empty. More resources can be allotted in frequencydomain for many-to-one mapping.

Further, for 30 kHz subcarrier spacing (first pattern), the first OFDMsymbols of the candidate RACH symbols in time domain have the OFDMsymbol indices {4, 8, 16, 20}+28*n within the half frame which containsthe RACH resources. For carrier frequencies smaller than or equal to 3GHz, n=0. For carrier frequencies larger than 3 GHz and smaller than orequal to 6 GHz, n=0, 1. For 30 kHz subcarrier spacing (second pattern),the first OFDM symbols of the candidate RACH symbols in time domain havethe OFDM symbol indices {2, 8}+14*n within the half frame which containsthe RACH resources. For carrier frequencies smaller than or equal to 3GHz, n=0, 1. For carrier frequencies larger than 3 GHz and smaller thanor equal to 6 GHz, n=0, 1, 2, 3. For 120 kHz subcarrier spacing, thefirst OFDM symbols of the candidate RACH symbols in time domain have theOFDM symbol indices {4, 8, 16, 20, 32, 36, 44, 48}+70*n within the halfframe which contains the RACH resources. For carrier frequencies largerthan 6 GHz, n=0, 1, 2, 3, 4, 5, 6, 7. For 240 kHz subcarrier spacing,the first OFDM symbols of the candidate RACH symbols in time domain havethe OFDM symbol indices {8, 12, 16, 20, 32, 36, 40, 44, 64, 68, 72, 76,88, 92, 96, 100}+140*n within the half frame which contains the RACHresources. For carrier frequencies larger than 6 GHz, n=0, 1, 2, 3.

The embodiments disclosed herein can be implemented through at least onesoftware program running on at least one hardware device and performingnetwork management functions to control the elements. The elements shownin the FIGS. 1 through 10 c include blocks which can be at least one ofa hardware device, or a combination of hardware device and softwaremodule.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the embodiments herein that others can, byapplying current knowledge, readily modify and/or adapt for variousapplications such specific embodiments without departing from thegeneric concept, and, therefore, such adaptations and modificationsshould and are intended to be comprehended within the meaning and rangeof equivalents of the disclosed embodiments. It is to be understood thatthe phraseology or terminology employed herein is for the purpose ofdescription and not of limitation. Therefore, while the embodimentsherein have been described in terms of preferred embodiments, thoseskilled in the art will recognize that the embodiments herein can bepracticed with modification within the spirit and scope of theembodiments as described herein.

Methods according to embodiments stated in claims and/or specificationsof the present disclosure may be implemented in hardware, software, or acombination of hardware and software.

When the methods are implemented by software, a computer-readablestorage medium for storing one or more programs (software modules) maybe provided. The one or more programs stored in the computer-readablestorage medium may be configured for execution by one or more processorswithin the electronic device. The at least one program may includeinstructions that cause the electronic device to perform the methodsaccording to various embodiments of the present disclosure as defined bythe appended claims and/or disclosed herein.

The programs (software modules or software) may be stored innon-volatile memories including a random access memory and a flashmemory, a read only memory (ROM), an electrically erasable programmableread only memory (EEPROM), a magnetic disc storage device, a compactdisc-ROM (CD-ROM), digital versatile discs (DVDs), or other type opticalstorage devices, or a magnetic cassette. Alternatively, any combinationof some or all of the may form a memory in which the program is stored.Further, a plurality of such memories may be included in the electronicdevice.

In addition, the programs may be stored in an attachable storage devicewhich is accessible through communication networks such as the Internet,Intranet, local area network (LAN), wide area network (WAN), and storagearea network (SAN), or a combination thereof. Such a storage device mayaccess the electronic device via an external port. Further, a separatestorage device on the communication network may access a portableelectronic device.

In the above-described detailed embodiments of the present disclosure, acomponent included in the present disclosure is expressed in thesingular or the plural according to a presented detailed embodiment.However, the singular form or plural form is selected for convenience ofdescription suitable for the presented situation, and variousembodiments of the present disclosure are not limited to a singleelement or multiple elements thereof. Further, either multiple elementsexpressed in the description may be configured into a single element ora single element in the description may be configured into multipleelements.

While the present disclosure has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope of the present disclosure. Therefore,the scope of the present disclosure should not be defined as beinglimited to the embodiments, but should be defined by the appended claimsand equivalents thereof.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A base station (BS) in a wireless communicationsystem the base station comprising: a transceiver; and at least oneprocessor operably coupled to the transceiver, wherein the at least oneprocessor is configured to: transmit, to a terminal, a beam failurerecovery configuration including: information on random access channel(RACH) resource for identifying a candidate beam associated withsynchronization signal block (SS block) resource or channel stateinformation-reference signal (CSI-RS) resource, a maximum number of RACHtransmissions for a beam failure recovery, a power ramping value, andinformation on a length of random access response (RAR) window; andreceive, from the terminal, a random access preamble for a beam failurerecovery request based on the candidate beam, wherein the information onthe length of the RAR window in the beam failure recovery configurationis a number of slots configured by the BS.
 2. The base station of claim1, wherein the candidate beam is identified based on a reference signalreceived power (RSRP) threshold configured for the beam failurerecovery.
 3. The base station of claim 1, wherein the beam failurerecovery configuration further includes a timer for beam failurerecovery.
 4. The base station of claim 1, wherein the RAR window is usedto monitor a response of the random access preamble for the beam failurerecovery.
 5. The base station of claim 1, wherein the information on theRACH resource for identifying the candidate beam associated with the SSblock resource includes SS block index and RA preamble index.
 6. Thebase station of claim 1, wherein the information on the RACH resourcefor identifying the candidate beam associated with the CSI-RS resourceincludes non-zero-power (NZP) CSI-RS Id and RA preamble index.
 7. Amethod performed by a base station (BS) in a wireless communicationsystem, the method comprising: transmitting, to a terminal, a beamfailure recovery configuration including: information on random accesschannel (RACH) resource for identifying a candidate beam associated withsynchronization signal block (SS block) resource or channel stateinformation-reference signal (CSI-RS) resource, a maximum number of RACHtransmissions for a beam failure recovery, a power ramping value, andinformation on a length of random access response (RAR) window; andreceiving, from the terminal, a random access preamble for a beamfailure recovery request based on the candidate beam, wherein theinformation on the length of the RAR window in the beam failure recoveryconfiguration is a number of slots configured by the BS.
 8. The methodof claim 7, wherein the candidate beam is identified based on areference signal received power (RSRP) threshold configured for the beamfailure recovery.
 9. The method of claim 7, wherein the beam failurerecovery configuration further includes a timer for beam failurerecovery.
 10. The method of claim 7, wherein the RAR window is used tomonitor a response of the random access preamble for the beam failurerecovery.
 11. The method of claim 7, wherein the information on the RACHresource for identifying the candidate beam associated with the SS blockresource includes SS block index and RA preamble index.
 12. The methodof claim 7, wherein the information on the RACH resource for identifyingthe candidate beam associated with the CSI-RS resource includesnon-zero-power (NZP) CSI-RS Id and RA preamble index.
 13. A terminal ina wireless communication system comprising: at least one processor; anda transceiver configured to: receive, from a base station (BS), a beamfailure recovery configuration including: information on random accesschannel (RACH) resource for identifying a candidate beam associated withsynchronization signal block (SS block) resource or channel stateinformation-reference signal (CSI-RS) resource, a maximum number of RACHtransmissions for a beam failure recovery, a power ramping value, andinformation on a length of random access response (RAR) window; andtransmit, to the BS, a random access preamble for a beam failurerecovery request by using on the candidate beam, wherein the informationon the length of the RAR window in the beam failure recoveryconfiguration is a number of slots configured by the BS.
 14. Theterminal of claim 13, wherein the at least one processor is furtherconfigured to identify the candidate beam based on reference signalreceived power (RSRP) threshold configured for the beam failurerecovery.
 15. The terminal of claim 13, wherein the at least oneprocessor is further configured to monitor a response of the randomaccess preamble for the beam failure recovery in the RAR window.
 16. Theterminal of claim 13, wherein the information on the RACH resource foridentifying the candidate beam associated with the SS block resourceincludes SS block index and RA preamble index.
 17. The terminal of claim13, wherein the information on the RACH resource for identifying thecandidate beam associated with the CSI-RS resource includesnon-zero-power (NZP) CSI-RS Id and RA preamble index.
 18. The terminalof claim 13, wherein the at least one processor is further configured totransmit, to the base station, the random access preamble for the beamfailure recovery until a timer for the beam failure recovery is expired.19. The terminal of claim 13, wherein if the terminal transmits a randomaccess preamble which is not changed from a previous transmitted randomaccess preamble for the beam failure recovery, a power ramping counterfor the random access preamble is increased by
 1. 20. The terminal ofclaim 13, wherein if a RAR reception is not successful or contentionresolution is not successful, a transmission counter for the randomaccess preamble is increased by 1.